I didn't see any 7-day, but my problem with RCCL and Carnival's cruises to Cuba is they stay one day in Havana. Carnival says "overnight" but they actually leave at 6 a.m. the next morning and since it is a people-to-people cruise, I can't imagine anyone getting off on their own to roam the city at nighttime unless you are with an excursion. RCCL and Carnival do not have dates open for later 2018. NCL actually stays in Havana two days (docking at 8 a.m. first day and leaving 5 p.m. the second day) and then goes to their island (it would be nice to see someone else's island for a change). I've been to Cozumel. I'd love to do the RCCL itinerary that includes Key West, but again I'd lose a day in Havana. Havana is more important to us than seeing anything else.
As far as being a smaller ship, it appears that RCCL and Carnival are using their older smaller vessels for Cuba. We booked for November 2018 on the NCL Sky (former Pride of Aloha). This ship is not small by any means and carries 2000 passengers. Granted, this itinerary is a pricy venture since I guess they have high port fees, etc. NCL does includes ALL drinks for this sailing, but upped your daily gratuity to include bartenders, but this is a unique cruise and an exciting experience and we get the extra day in Havana. The cabins are much smaller than we are used to, so we did book a balcony since it was only $300 more and there are three of us in the cabin. We can't wait.